1. Field of the Invention
This invention relates to light-shaders and particularly to light-shaders placed in front of the faceplates of television receiving sets or computer displays or to light-shaders used as indicative plates of various warning lamps.
2. Description of the Prior Art
Conventionally, light-shaders are used in order to prevent the deterioration of the contrast in faceplates caused due to the incidence of outer light by regulating the outer lights incident onto faceplates of various displays such as cathode ray tubes of television receiving sets and computer displays, and liquid crystal displays or to prevent the reflection of lights from faceplates onto reflective surfaces of surrounding objects by limiting the diffusion angle of the light from the faceplates within a certain value.
For example, FIGS. 1 and 2 illustrate a prior art light-shader 1 (See Japanese published unexamined application for patent No. 57-189439). This light-shader 1 comprises a transparent substrate 2 and a light-shading film 3 formed on the substrate 2. The light-shading film 3 is produced by the following steps of applying liquid photosensitive resin containing silica particulates to the substrate 2, transmitting ultraviolet rays onto the resulting continuous layer of the photosensitive resin through a negative film containing a corresponding screening pattern eliminating unexposed parts of the layer of the photosensitive resin, and opaquely coloring only many exposed square walls of the layer of the photosensitive resin to be opaque. The many square opaque walls of the light-shader 3 can regulate outer light falling onto the substrate 2 at relatively large angles.
FIG. 3 illustrates another prior art light-shader 4 (See Japanese published unexamined application for patent No. 51-75456). This light-shader 4 comprises transparent thermoplastic resin layers 5, light-diffusive layers 6 and colored opaque adhesive layers 7. This light-shader 4 is produced by the steps of forming a block of a structure corresponding to that of the light-shader 4 and planing the block. The light-diffusive layers 6 and the colored opaque adhesive layers 7 can regulate outer light falling at relatively large angles.
However, the prior art light-shaders 1 and 4 produce many moires in combination with the faceplate and make the outlines of images in the faceplate unclear. If the orientations of the overall opaque parts of the light-shaders 1 and 4 are set at more than certain angles with the orientation of fluorescent substances in the faceplate of the television receiving set in order to prevent the production of moires, then it causes images in the faceplate of the television receiving set to be devastated.
FIGS. 4 to 6 illustrate an automotive instrument panel using another prior art light-shader. The instrument panel 10 comprises a speedometer 11, a tachometer 12, an odometer 13, a tripmeter 14, a clock 15, a display 16 of a drive computer and warning lights 17. The indicative parts of these devices have essentially the same structure and only the warning light 17 (e.g. as a fuel alarm) is described below.
As shown in FIG. 6, the warning light 17 comprises a light source 18 and an indicative panel 19. This indicative panel 19 comprises a colored translucent polycarbonate panel 20 with a smooth outer surface 20a, a color-pigment layer 21 printed onto an inner surface of the panel 20, a printed indicative layer 22 sandwiched between the color-pigment layer 21 and the panel 20, and a light source 18 facing the color-pigment layer 21. The transmissivity of the panel 20 is 15%. The indicative layer 22 contains a warning symbol 23. When an alarm indicating, e.g. that fuel is low is to be sent out, the light source 18 turns on and thus illuminates the warning symbol 23 by its radiant light L.sub.2 in order to warn to a driver 35. In this indicative panel 19, the outer surface 20a of the polycarbonate panel 20 reflects most of outer light L.sub.1, thus reducing the contrast ratio of the indicative panel 19 and the visibility of the warning symbol 23. In addition, the indicative layer 22 diffuses the radiant light L.sub.2, thus reducing the visibility of the warning symbol 23.